In recent years, for example, in an electronic device such as an electric power steering apparatus used for a vehicle, a power circuit for which a so-called power semiconductor or the like is used or an electronic circuit such as an inverter circuit in which large power is used is formed as a power substrate on which these power semiconductors are collectively formed to meet a demand for miniaturization of the electronic devices including the electronic circuit. An electronic circuit in which the large power is used and an electronic circuit in which a small power is used are used as separated substrates and converted into dedicated substrates.
Further, it is an important problem to efficiently dissipate heat generated due to a loss of the highly density mounted power semiconductor to convert the circuits for which the power semiconductors are used into the dedicated substrates.
Conventionally, for such a dedicated substrate (power substrate), a substrate formed by pasting a conductor foil (made of copper) on a surface of a metal supporting plate made of a material such as aluminum with an insulating layer interposed therebetween, etching this conductor foil and forming wiring patterns is used. The power semiconductor and various electronic parts are mounted on the substrate to form a circuit.
However, according to the above configuration, the wiring patterns are formed by etching. Therefore, when the thin conductor foil which is approximately 70 [μm] is used, and is used for a circuit for which the power semiconductor in which a large current flows is used, a wiring resistance causes a problem. Further, according to the above configuration, a heat dissipation characteristic is limited by the insulating layer of a low heat transfer coefficient. Therefore, there is a problem that it is not possible to provide a sufficient performance.
Further, when the electronic parts such as the power semiconductor are collectively mounted on the wiring patterns, an interaction between the wiring patterns such as impedance and inductance characteristics produced by the wiring pattern also need to be taken into account.
Hence, for example, Japanese Patent No. 3855306 B2 (Patent Document 1), Japanese Unexamined Patent Publication No. 2014-72316 A (Patent Document 2), Japanese Unexamined Patent Publication No. 2013-125848 A (Patent Document 3) and WO 2009/110376 A1 (Patent Document 4) disclose techniques to solve the conventional problems.
The technique disclosed in Patent Document 1 relates to an electronic part mounting heat-dissipating substrate. The electronic part mounting heat-dissipating substrate includes a metal plate which is punched in a predetermined wiring pattern shape, and a composite insulating material which is integrally molded with the metal plate and has a high heat conductivity. This technique adopts a structure in which at least a part mounting portion of the metal plate is exposed from the composite insulating material, and a heat-generating part arrangement portion of the part mounting portion is provided with a step-processed portion. Further, Patent Document 1 discloses that the step-processed portion of the electronic part mounting heat-dissipating substrate makes thin the composite insulating material formed at a lower portion of the heat-generating part arrangement portion, the heat is dispersed by a metal plate and is dissipated by an insulating material of the high heat conductivity as a result, and therefore the heat dissipation is good.
Furthermore, the technique disclosed in Patent Document 2 employs a configuration where, when a power module which drives an electric motor is formed, a pair of upper and lower switching elements are disposed adjacent to a power block and a ground block inside the power module, a power terminal connected to a power supply, a ground terminal connected to a ground and control terminals of a pair of switching elements are disposed apart from each other. Still further, Patent Document 2 discloses that, according to the technique disclosed in Patent Document 2, the control terminals, the power terminals and the ground terminals are disposed apart from each other as described above, so that it is possible to realize the power module which can reduce a loss and a noise.
Moreover, an object disclosed in Patent Document 3 is to solve a problem that miniaturizing a size of the power module to miniaturize a package case of a power device for which a silicon-carbide device is used narrows an inter-terminal distance and is likely to cause a discharge phenomenon between terminals. Further, to solve the problem, Patent Document 3 discloses a power module semiconductor device which includes “a substrate, a low voltage-side gate terminal electrode which is disposed on a first side of the substrate, a low voltage-side source terminal electrode which is disposed on the first side, and is disposed adjacent to the low voltage-side gate terminal electrode, a high voltage-side gate terminal which is disposed on the first side, and is disposed apart from the low voltage-side gate terminal electrode and the low voltage-side source terminal electrode, a high voltage-side source terminal electrode which is disposed on the first side, and is disposed adjacent to the high voltage-side gate terminal electrode, an output terminal electrode which is disposed on a second side different from the first side of the substrate, a power voltage supply terminal electrode which is disposed on a third side of the substrate different from the first side and the second side, and a ground potential electrode which is disposed on the third side and is disposed apart from the power voltage supply terminal electrode”. Patent Document 3 discloses that it is possible to lead the terminal electrode of the power module semiconductor device from three directions of the mold package and secure an insulating distance.
Further, Patent Document 4 discloses a technique related to a lead frame substrate. The lead frame substrate includes plural independent patterns which retain electronic parts, and resin bonding members which are filled in gaps between the adjacent patterns to mutually connect the adjacent patterns. The resin bonding members protrude closer to a thickness direction than a top surface position of the patterns is. A back surface of the substrate is provided with a metal base plate and a metal cooling fin with a thermal conductive resin sheet interposed therebetween.